Touch sensitive devices such as touch screens are widely used as input devices for providing instructions to an electronic device, like a mobile phone, an electronic book reader, a laptop or vending and automatic teller machines. Various technologies exist to enable this functionality, like the capacitive or resistive touch sensitive technology but also acoustic based technologies based on surface acoustic waves or on bending waves propagating inside the interaction surface.
Touch sensitive devices based on bending waves determine a position of an impact on a touch sensitive surface of the device based on the analysis of the propagation of the bending wave created due to the impact realized by the user when touching the touch sensitive interaction surface. EP 1512116 A1 describes such a method.
An important functionality of the touch sensitive device is the capability to discriminate a simple touch event corresponding to a simple tap from a touch-and-hold event during which the user keeps his finger in contact with the touch sensitive interface to provide a different instruction to the device compared to the simple touch event. This is comparable to a mouse click and a mouse click down action.
To provide this functionality, EP 2 214 082 A1 proposed to combine the acoustic technology responsible for determining the touch location with a capacitor, responsible for determining the hold part of the touch event by identifying a capacitance change. Another solution is disclosed in prior art document US2006/0262104 proposing to analyse the frequency spectrum of the sensed acoustic signal to discriminate between touch down and touch-and-hold or to inject acoustic waves propagating inside interaction surface and to determine changes in the wave pattern.
It appears that the integration and/or calibration of these technologies are not always straight forward and not universal. Indeed, the response of the acoustic interface to injected acoustic waves into the interaction surface will strongly depend on the material used but also on the geometry of the device which could lead to unwanted reflections.
It is therefore a first object underlying this invention to provide a method that is capable of discriminating between touch events and touch-and-hold events that can be incorporated in a simple way into touch sensitive devices.
The use of touch sensitive devices is sometimes limited by particular properties of the electronic device into which the touch sensitive device is incorporated. This is, for instance, the case for clamshell laptop. Users of a clamshell laptop device are hesitating to use a touch sensitive functionality of the laptop screen due to a lack of a rigid support of the screen.
It is therefore a second object underlying this invention to provide an electronic device and corresponding method that provides a way to interact with the device similar to a touch sensitive device without, however, needing a physical contact between the user and the device.